BR112012017704B1 - two-wheel vehicle tire comprising a tread with incisions - Google Patents

Abstract

TWO-WHEEL VEHICLE TYPE BEARING A Treadmill WITH INCISIONS. The invention relates to a two-wheel motor vehicle tire with a tread, comprising at least one incision (5) and in a circumferential plane, at least a portion of a wall of said at least one incision forms an angle with the radial direction comprising between 5 and 45 ° and the angle formed between at least a portion of a wall of said at least one incision and the radial direction in a circumferential first plane is different from the angle formed between at least a portion of a wall of said at least one incision and the radial direction in at least one circumferential second plane.

Description

TWO-WHEEL VEHICLE TIRE UNDERSTANDING A Treadmill WITH INCISIONS

[0001] The invention relates to a tire intended to equip a vehicle and, more particularly intended to equip a two-wheeled vehicle, such as a motorcycle and even more specifically a tire intended to equip a motorcycle with a higher speed index. the W which corresponds to a speed of 270 km / h.

[0002] Although not limited to such an application, the invention will be more particularly described with reference to such a motorcycle or motorcycle tire, and even more specifically, with reference to a tire intended to be fitted to the front wheel.

[0003] As in the case of all other tires, we can see a "radialization" of motorcycle tires, the architecture of such tires comprises a frame reinforcement formed from one or two layers of reinforcement elements that form with the steering circumferential an angle that can be between 65 ° and 90 °, of said carcass reinforcement, being radially mounted by a reinforcement crown formed by reinforcement elements. There are, however, non-radial tires which also refer to the invention. The invention also relates to partially radial tires, that is, whose reinforcement elements, of the carcass reinforcement, are radial over at least a portion of said carcass reinforcements, for example, in the part corresponding to the tire crown.

[0004] Many crown reinforcement architectures have been proposed, depending on the tire that is intended to be mounted on the front of a motorcycle or on the back. A first structure consists, by said reinforcement crown, of using only circumferential cables, and said structure is more particularly used for the rear position. A second structure, directly inspired by the structures commonly used in passenger car tires, was used to improve wear resistance, and consists of using, at least two layers of working crowns, the reinforcement elements substantially parallel to each other, in each layer, more crossed from one layer, to the next, making the sharp angles of such tires with the circumferential direction, and being more particularly suitable for the front of the bikes. Said two layers of working crowns can be associated with at least one layer of circumferential elements, generally obtained by helically winding a strip of at least one reinforcement element coated with rubber.

[0005] The choice of tire crown (dome) architectures directly affects certain tire properties, such as wear, resistance, grip, or even comfort during the trip or especially in the case of motorcycles, including the stability. However, other tire parameters, such as the nature of the rubber compounds that make up the tread, also intervene on the properties of said tire. The selection and nature of the rubber compounds that make up the tread are, for example, of essential parameters regarding wear properties. The choice and nature of the rubber compounds that make up the tread and also influence the tire's grip properties.

[0006] Other types of tires are also known with tread treads comprising incisions, more particularly for tires intended to run on snow-covered soils, with icy or wet surfaces.

[0007] Such treads are usually provided with raised elements of the type ribs or blocks separated from each other, in the circumferential and / or transverse direction by transverse and / or circumferential grooves. These treads then comprise incisions or crevices, the widths of which are different from zero and much smaller than the previously mentioned grooves. By making a plurality of cuts leading to the rolling surface, a plurality of gum edges are created to cut the water layer that may be present on the road, in order to keep the tire in contact with the ground and create cavities eventually forming ducts to collect and evacuate the water present in the tire's contact area with the ground when they are arranged to drive outside the contact area.

[0008] Numerous types of incisions have already been proposed in order to improve the tire's grip on the soils under consideration.

[0009] FR 2 418 719 describes, for example, the incisions that may be normal to the tread surface or inclined in relation to the direction perpendicular to said surface.

[0010] FR 791 250 describes the incisions with a wavy line on the tread surface.

[0011] The performance of motorcycles today leads to want better control in handling vehicles, especially in the case of certain uses and, eventually, being able to offer different tires to rotate in the front, depending on the use.

[0012] As mentioned earlier, the architecture of the tire crown reinforcement or the nature of the rubber compounds in the tread may allow such effects to be obtained.

[0013] It can also be sought to provide tire behavior that may vary depending on the axial direction of the tire.

[0014] With reference to the handling of the vehicle, the inventors wish to offer pilots more precision when returning the effort with the handlebars, either increasing or decreasing, depending on the use made of the vehicle.

[0015] The invention thus aims to provide a motorcycle tire whose properties in terms of handling or return of efforts at the level of handlebars are improved.

[0016] This objective was achieved according to the invention, by a tire for a motor vehicle with two wheels comprising a reinforcement structure of the carcass type, formed of reinforcement elements, anchored on each side of the tire to a bead whose base is intended for be mounted on a rim base, each bead extending radially outward, by a flank, and the flanks grouting radially outwards on the tread; the tread comprising at least one incision and, in the circumferential plane, at least a portion of a wall of said band, at least one incision forming an angle with the radial direction comprised between 5 and 45 ° and said angle formed between at least at least a portion of a wall of said band with at least one incision and in the radial direction in a first circumferential plane being different from the angle formed between at least a portion of a wall of said band with at least one incision and the radial direction in one, at least, according to circumferential plane.

[0017] As defined by the invention, an incision is a cut forming two walls and the distance between the walls measured according to a normal plane tangential to one of the walls is less than 1.5 mm and preferably less than 1 mm. Said distance at the level of the tread surface is at least equal to said distance, at the level of the bottom of the incision, that is, the level furthest from the surface of the tread. Particularly in the case of a motorcycle tire, the tread thickness is relatively unimportant, an extension of the said distance from the tread surface to the bottom of the incision cannot exist under the risk of causing the edges of the tire to sag. incision at the level of the tread surface and thus lead to a decrease in the surface area of the contact with the ground.

[0018] The longitudinal direction of the tire, or circumferential direction is the direction corresponding to the periphery of the tire and defined by the direction of rotation of the tire.

[0019] The transversal or axial direction of the tire is parallel to the axis of rotation of the tire.

[0020] The axis of rotation of the tire is the axis around which it rotates in normal use.

[0021] A circumferential plane or circumferential cutting plane is a plane perpendicular to the axis of rotation of the tire. The equatorial plane is the circumferential plane passing through the center or the top (crown) of the tread.

[0022] A radial or meridian plane containing the tire's axis of rotation.

[0023] The radial direction is a direction that crosses the axis of rotation of the tire and is perpendicular to it. The radial direction is the intersection between a circumferential plane and a radial plane.

[0024] A tire thus made according to the invention and mounted on the front wheel of a motorcycle effectively provides the rider with a return to the handlebars other than that which provides a tire that does not include any incisions or that contains incisions without inclination, that is, in a plane circumferential, no part of an incision wall does not form an angle with the radial direction between 5 and 45 °. The inventors believe that thus, they demonstrate that the inclination variable, as proposed, according to the invention, of the incision with respect to the radial direction in the circumferential cutting plane, modifies the return of efforts on the handlebars, that is, they state that the reaction of the tire through the contact area does not resent the driver.

[0025] Advantageously for allowing the pilot to be sensitive to the return of efforts on the handlebars, in a circumferential plane, given the angle formed between at least a portion of an incision wall and the radial direction being identical for all incisions having a intersection with said plane.

[0026] The angle formed between at least a part of a wall of said initiation and the radial direction in a first circumferential plane, being different from this formed in at least a second circumferential plane, means that according to the curvilinear abscess of a wall of said incision, said angle formed between at least part of an incision wall and the radial direction is variable.

[0027] Depending on the variants of the invention, this angle can vary continuously or be constant according to at least part of the curvilinear abscess.

[0028] The variation of the incision inclination relative to the radial direction in a circumferential cutting plane according to the invention over the incision length is obtained by combining the choice of the angle formed between at least part of an incision wall and the direction radial, the impact of the orientation of the incision itself in relation to the circumferential direction and the impact of the tire shape is in particular the very axial curved profile.

[0029] This variation of angle according to the curvilinear abscess of a wall of the said incision allows to adapt the effort returns to the level of the handlebar according to the position of the motorcycle in terms of curvature, that is, as the vehicle goes in a straight line or performs well a curve.

[0030] According to a proposed embodiment of the invention, at least a part of a wall of at least one incision forming an angle with the radial direction comprised between 5 and 45 ° is in contact with the area of friction. According to this proposed embodiment of the invention, if only a part of the incision wall is inclined, it is a part of the incision that comes into contact with the area of friction.

[0031] It can also, effectively, be advantageous from an industrial point of view, to limit the inclination of the incision in its portion that leads to the tread, while the deepest part is not inclined in order to limit the efforts exerted , to open the cooking mold after the tire is vulcanized.

[0032] According to other embodiments of the invention, the incision can be tilted over its entire height, or depth. The portion of the mold that penetrates the tire to form said incision may then be easier to make.

[0033] According to other embodiments of the invention, the incision may be inclined over only a part of its length, especially when a part of the incision is oriented in a direction that approaches the circumferential direction, the incision may advantageously not be inclined.

[0034] According to a predicted embodiment of the invention, the difference between the angle formed between at least part of a wall of said incision and the radial direction in a first circumferential plane being this formed in a second circumferential plane greater than 10 ° .

[0035] According to a variant and advantageous embodiment of the invention, when particularly the main direction on the tread surface of at least one incision shape, forms at least locally with the circumferential direction an angle greater than 70 °, the angle formed between at least part of a wall of at least one incision and in the radial direction is less than 30 ° in a circumferential plane located in the incision zone, where it forms an angle greater than 70 ° with the circumferential direction.

[0036] The inventors were able to demonstrate that an angle of inclination less than 30 ° has a sufficiently noticeable effect on the return of efforts on the handlebars, when the incision presents an angle with the circumferential direction greater than 70 °. According to other embodiments of the invention, the inclination angles can, however, be considered to obtain the even more important effects on the return of the efforts with the handlebars.

[0037] According to another embodiment of the invention, when the main direction on the tread surface of said at least one incision shape at least locally with the circumferential direction having an angle less than 30 °, the angle formed between at at least a portion of a wall of said at least one incision and the radial direction is greater than 35 ° in a circumferential plane located in the area of the incision, where it itself forms an angle less than 30 ° with the circumferential direction.

[0038] The inventors have demonstrated that when the incision has an angle with the circumferential direction of less than 30 °, the angle of inclination of the incision above 35 ° is necessary to obtain a significant effect on the return of efforts on the handlebars.

[0039] Depending on the variants, it is then possible to obtain effects on the return of the efforts on the handlebars, which will be substantially homogeneous with the incisions whose main direction on the tread surface varies due to the variation of the inclination of said incision along its main direction, the angle formed between at least a portion of a wall of said at least one incision and the radial direction being greater than 35 ° in a circumferential plane when the main direction on the tread surface of said at least one shape of incision with the circumferential direction an angle less than 30 ° and the angle formed between at least a portion of a wall of said at least one incision and the radial direction being less than 30 ° in a circumferential plane when the main direction on the surface of the tread of said at least one incision forms an angle greater than 70 ° with the circumferential direction.

[0040] A first embodiment of the invention provides that the orientation of the angle formed between at least part of a wall of said at least one incision and the radial direction is identical to the direction of rotation of the tire.

[0041] The inventors were also able to demonstrate that, depending on the different parameters that make up the tire, such an orientation of the incision inclination allows either to increase the effort yields on the handlebars, or to decrease them. In fact, depending on the choice of materials that make up the tread, the type of reinforcement architecture, whether it is the orientation or the nature of the reinforcement elements, the tire profile, notably according to the axial direction, the returns of the Handlebar efforts can vary and it can be interesting to either increase or decrease the return on these efforts.

Accordingly, according to another embodiment of the invention, the orientation of the angle formed between at least a portion of a wall refers at least to an incision and the radial direction is opposite to the direction of rotation of the tire.

[0043] According to other embodiments of the invention, the tread being constituted by at least one central part and two axially outer parts, each part comprises at least one part of an incision and, at the level of the surface of the tread. rolling, the orientation of the angle formed between at least a part of a wall of said at least a part of an incision and the radial direction in the central part is opposite to the orientation of the angle formed between at least a part of a wall of said at least a part of an incision and the radial direction in the axially outer parts.

[0044] According to this variant of the invention, when the stress returns are homogeneous over the axial width of the tire, it is possible to modify the stress returns on the handlebars by increasing or decreasing them as the motorcycle is driven in a straight line or that it is guided in a curve. In a straight line, the contact area corresponds to the central part of the tread and in curve, the contact area is moved according to the axial direction to one or the other of the two axially outer parts.

[0045] We will preferentially seek to increase the efforts of return on the handlebars on the central part of the tread to notably decrease the maneuver at a high speed and to decrease them on the two axially outer parts to on the contrary, improve the maneuver in curves.

[0046] According to a predicted embodiment of the invention, the difference between the angle formed between at least part of a wall of said at least one incision and the radial direction in a circumferential first plane passing through the central part and this formed in a second circumferential plane belonging to an axially outer part is greater than 10 °.

[0047] According to a first embodiment of the invention, the smallest angle formed between at least part of an incision wall and the radial direction in a circumferential plane passing through the central zone of the central part of the tire's tread is greater at the greatest angle formed between at least part of an incision wall and the radial direction in a circumferential plane passing through the axially outer part of an axially external part of the tire tread.

[0048] The central part of the tread is axially bounded by the axially outermost points of the contact area corresponding to a run in a straight line. The axially outer parts of the tire tread correspond to the parts of the tread outside the central part.

[0049] The central zone of the central part is axially bounded on both sides of the median plane in a radial plane, over the surface of the tread, by a point distant of a quarter of the width of the central part of the tread of the plane medium tire.

[0050] The axially outer zone of an axially outer part of the tire tread is bounded axially in a radial plane by a point a quarter of the width of the tread contact area from the point axially the outermost of the area contact contiguously with the axially outer part.

[0051] The contact area corresponding to running in a straight line is measured by vertical crushing in a direction perpendicular to the axis of rotation of the tire (meaning that the crushing is carried out vertically, the wheel being in a vertical plane) the tire mounted on a nominal rim recommended by ETRTO, inflated to 2.5 bars on a non-lubricated plate with a load corresponding to 60% of the maximum recommended tire load (load index).

[0052] According to a second embodiment of the invention, the greater angle formed between at least part of an incision wall and the radial direction in a circumferential plane passing through the central zone of the central part of the tire's tread is less at the smallest angle formed between at least part of an incision wall and the radial direction in a circumferential plane passing through the axially outer part of an axially outer part of the tire tread.

[0053] One or other of these embodiments can be particularly chosen depending on the desired return to the handlebars.

[0054] For the purposes of the invention, according to the embodiments of the invention, the notions of greater angle and of lesser angle are considered in absolute values.

[0055] As explained earlier, depending on the constitution of the tire, but also depending on the use to be made, it is possible to choose an orientation of the angle formed between at least a portion of a wall, of which at least one portion refers of the incision and in the radial direction in the central part, in the same direction as the direction of the bearing and an opposite angle in the two axially outer parts or also to provide the opposite.

[0056] An advantageous form of the invention provides that the depth of the incisions varies according to the axial direction, in particular because it takes into account different speeds of use, according to the axial direction of the tire and to obtain the stiffness of the tread variables according to the axial direction.

[0057] According to an advantageous variant of the invention, at least the tread surface is composed of a first polymeric compound extending over at least a portion of the central part and at least a second polymeric compound having physico-chemical properties. chemicals other than said first polymeric compound and covering at least a portion of the axially outer parts of the tread.

[0058] Such a variant of the invention allows the realization of a tread having, for example, improved relative wear properties in the center of the tread and properties related to improved adhesion on the axially outer parts.

[0059] As explained earlier, the nature of the polymeric compounds that make up the tread can have an effect on stress returns on the handlebars. The presence of different compounds may lead to want to increase and / or decrease depending on the vehicle's use and in particular when driving in a straight or curved line. Depending on the nature of the compounds, it may then be necessary, according to the invention, to have angles of inclination of the incisions in the same direction over the entire width of the tread to obtain similar or opposite effects or to have angles of inclination of the incisions in opposite directions in the central part. and on the axially outer parts equally to obtain similar or opposite effects.

[0060] According to an embodiment of the invention, to give a more profitable shape to the symmetrical properties of the tire, the central circumferential band is advantageously preferably centered on the equatorial (horizontal) plane. According to other embodiments, designed for example, in front of the rolling tires on a circuit comprising the turns essentially in the same direction, the circumferential central strip may not be centered on the equatorial plane.

[0061] Advantageous embodiments of the invention may provide for the presence of five or more circumferential bands to form at least one surface of the tread and, therefore, confer a gradual evolution of the properties of said tread from the equatorial plane to the shoulders. As previously seen, such an implementation can be symmetrical in relation to the equatorial plane or not, the distribution of different bands in its composition, that is, by distribution in relation to the equatorial plane.

[0062] According to a proposed embodiment of the invention, the second polymeric compound is of a different composition from that of the first polymeric compound and more preferably, the second polymeric compound has adhesion properties superior to those said to the first polymeric compound.

[0063] According to other embodiments, different properties can be obtained with identical compounds through different vulcanization conditions.

[0064] Still advantageously, the radial thicknesses of the first and second polymeric compounds can be different, in order to axially optimize the tread wear. Advantageously, the thicknesses vary gradually.

[0065] According to an embodiment of said invention, the second polymeric compound has a Shore A hardness, different from that of the first polymeric compound.

[0066] Shore A hardness of polymeric compounds after vulcanization (cooking) is evaluated according to ASTM D 2240-86.

[0067] According to a standard embodiment of the invention, the reinforcing elements of the reinforcement structure of the carcass type, make the circumferential direction an angle between 65 ° and 90 °.

[0068] According to a variant of the invention, the reinforcement structure of the crown comprises at least one layer of reinforcement elements that form angles with the circumferential direction comprised between 10 ° and 80 °.

[0069] According to this embodiment, the crown reinforcement structure advantageously comprises at least two layers of reinforcement elements, the reinforcement elements forming angles between 20 ° and 160 ° between them, from one layer to the next, and preferably greater than 40 °.

[0070] According to a standard embodiment of the invention, the elements for strengthening the working layers are made of textile material.

[0071] In accordance with another embodiment of the invention, the elements for strengthening the working layers are made of metal.

[0072] In an advantageous embodiment of the invention, notably to optimize the stiffness of the reinforcement structure along the meridian (vertical) of the tire, and in particular the edges (edges) of the working layers, the angles formed by elements of reinforcement of the working layers with the longitudinal direction are variable according to the transverse direction in such a way that said angles are higher at the axially outer edges (edges) of the layers of reinforcement elements in relation to the angles measured at the level of the equatorial plane of the tire.

[0073] As explained previously, in the case of polymeric compounds from different tread, variations in the angles of the reinforcement elements of the working layers can modify the return of effort on the handlebars, according to the axial direction.

[0074] Such variations in the angles of the reinforcement elements of the working layers may lead to wanting to increase or decrease the return of efforts on the handlebars according to the use of the vehicle and especially when driving in a straight line or in a curve. Depending on the nature of the reinforcement elements and the variations in the angles according to the axial direction, it may then be necessary, according to the invention, to have the angles of inclination of the incisions in the same direction along the entire width of the tread to achieve effects similar or opposite, or also have angles of inclination of the incisions in opposite directions in the central part and in the axially outer parts equally to obtain similar or opposite effects.

[0075] An embodiment of the invention provides that the tire in particular consists of a crown reinforcing structure that comprises at least one layer of circumferential reinforcing elements; according to the invention, the layer of circumferential reinforcement elements is composed of at least one reinforcement element oriented at an angle with the longitudinal direction less than 5o.

[0076] Preferably also, the reinforcing elements of the layer of circumferential reinforcing elements are metallic, and / or textile, and / or glass. The invention notably provides for the use of reinforcement elements of different natures in the same layer of circumferential reinforcement elements.

[0077] More preferably, the reinforcing elements of the layer of circumferential reinforcing elements have an elastic modulus greater than 6000 N / mm2.

[0078] An alternative embodiment of the invention advantageously provides that the circumferential reinforcing elements are distributed in the transverse direction with a variable pitch.

[0079] The variation of the pitch between the circumferential reinforcement elements is reflected by a variation in the number of circumferential reinforcement elements per unit length according to the transverse direction and, consequently, by a variation in the density of circumferential reinforcement elements according to the transverse direction and, therefore, by varying the circumferential stiffness according to the transverse direction.

[0080] As explained earlier, in the case of different tread polymer compounds, the variations in the angles of the reinforcement elements of the working layers, the variation of the pitch according to the axial direction between the circumferential reinforcement elements can alter the returns of the efforts on the handlebars according to the axial direction.

[0081] Such variations in pitch (tone) of circumferential reinforcement elements may lead to wanting to increase and / or decrease the return of efforts on the handlebars according to the use of the vehicle and notably its driving in a straight or curved line. Depending on the nature of the reinforcement elements and the pitch variations according to the axial direction, it may then be necessary according to the invention to have incision inclination angles in the same direction along the entire tread to obtain similar or opposite effects or also have angles of inclination of the incisions in opposite directions in the central part and in the axially outer parts equally to obtain similar or opposite effects.

[0082] The invention also provides a combination of angle of inclination of the incisions in the same direction over the entire width of the tread or also the angle of inclination of the incisions in opposite directions in the central part and in the axially outer parts in order to obtain effects similar or opposite, with the set or simply some of the different parameters previously mentioned which are different polymeric compounds in the central portion and in the axially outer parts of the tread, the angles formed by elements of reinforcement of the working layers with the variable longitudinal direction as the transverse direction, and a variation in pitch (tone) according to the axial direction between the circumferential reinforcing elements.

[0083] Other details and advantageous features of the invention appear from the following description of embodiments of the invention, with reference to Figures 1-4 which represent:
Figure 1 is a partial perspective view of a diagram of a tire according to a first embodiment of the invention,
Figure 2 is a partial perspective view of a diagram of a tire according to a first embodiment of the invention indicating the measurement of an angle at a point,
Figure 3a, a partial perspective view of a diagram of a tire according to a second embodiment of the invention showing the measurement of an angle at a point,
Figure 3b is a partial perspective view of a tire diagram according to the second embodiment of the invention indicating the measurement of an angle at a second point,
Figure 3c is a partial perspective view of a tire diagram according to the second embodiment of the invention indicating the measurement of an angle at a third point,
Figure 4a, is a partial perspective view of a diagram of a tire according to a third embodiment of the invention indicating the measurement of an angle at a point,
Figure 4b is a partial perspective view of a diagram of a tire according to the third embodiment of the invention indicating the measurement of an angle at a second point.

[0084] Figures 1 to 4 are not represented in scale to simplify the understanding.

[0085] Figure 1 shows a partial perspective view of a tire 1, and more precisely of the outer surface 2 of its tread, intended to equip the front wheel of a motorcycle. Tire 1 has a curvature value greater than 0.15, and preferably greater than 0.3. The curvature value is defined by the Ht / Wt ratio, that is to say, by the ratio of the tread height to the maximum width of the tire's tread.

[0086] In a manner not shown in the figures, tire 1 comprises a reinforcement of the carcass consisting of a layer comprising reinforcement elements of the textile type. The layer is formed by radially arranged reinforcement elements. The radial positioning of the reinforcement elements is defined by the angle of placement of said reinforcement elements; a radial arrangement corresponds to an angle of placement of said elements with respect to the longitudinal direction of the tire comprised between 65 ° and 90 °.

[0087] The reinforcement of the carcass is anchored on each side of tire 1 in a bead whose base is intended to be mounted on a rim base. Each bead is extended radially outwards by a flank, said flanks joining radially to the outside of the tread.

[0088] Tire 1 further comprises a crown armor formed for example of two layers of reinforcement elements forming angles with the circumferential direction, said reinforcement elements being crossed from one layer to the next, forming angles between them. for example 50 ° in the region of the equatorial plane, the reinforcing elements of each layer forming an angle of, for example, equal to 25 ° with the circumferential direction.

[0089] The crown reinforcement may also consist of a layer of circumferential reinforcement elements instead of layers of reinforcement elements forming angles with the circumferential direction or in combination with them.

[0090] The tread 2 of tire 1 comprises a sculpture consisting of continuous grooves 3 circumferentially oriented and transversal grooves 4, the main direction of which having a slight angle with the radial direction to give an orientation to said sculpture. This orientation of the sculpture in the case of a tire equipped with a front wheel is usually such that the direction of orientation of the sculptures is opposite to the direction of rotation of the tire.

[0091] According to the invention, the tread comprises incisions or grooves 5, whose non-zero widths are much smaller than those of grooves 3 and 4 mentioned above. These form, in accordance with the invention, in a circumferential plane, an angle with the radial direction comprised between 5 and 45 °, about which is seen in the description of Figure 2.

[0092] Figure 2 represents a partial perspective view of a tire 21 similar to that of Figure 1 and which differs by a less detailed representation of the grooves and in the presence of a single incision 25 whose tracing on the surface of the tread 22 forms a curve.

[0093] In Figure 2, a meridian plane 26 and an equatorial plane 27 are shown whose intersection forms a straight line 28 radially oriented and cutting the incision 25 at a point "O" on the tread surface 22.

[0094] The straight line 28 forms at point "O" an angle δ with curve 29, which represents the intersection of the equatorial plane 27 with incision 25. This angle δ has a value of 34 °.

[0095] In figures 3a, 3b and 3c there is shown a partial perspective view of a tire 31 similar to that of figure 2, and which differs by the presence of an incision 35 that traces an “S” shape over the tread 32 .

[0096] In figure 3a, a meridian plane 36 and the equatorial plane 37 are represented whose intersection forms a straight line 38 radially oriented and cutting incision 35 at a point "A" on the tread surface 32.

[0097] The straight line 38 forms at point A, an angle with a curve 39, which represents the intersection of the equatorial plane 37 with the incision 35. This angle "a" has a value of 9o.

[0098] Figure 3b shows an angle a 'at a point A' between a straight line 39 'and a curve 38', these curves being defined as in the case of figure 3a, more from another circumferential plane 37 'axially translated in relation to the equatorial plane 37 and from another meridian plane 36 'translated circumferentially in relation to the plane 36 of Figure 3a such that the straight line 38' cuts the incision 35 at point A 'of the tread surface 32. The angle a 'has a value of 17 °.

[0099] Figure 3c shows an angle a "at a point A" between a line 39 "and a curve 38", these curves are defined as in the case of figures 3a and 3b, more from another circumferential plane 37 " axially translated with respect to the equatorial plane 37 and from another meridian plane 36 "circumferentially translated with respect to the planes 36 and 36 'of Figures 3a and 3b, such that line 38" cuts incision 35 at point A "of the surface of the tread band 32. The angle a "has a value of 23 °.

[00100] When designing the mold for the production of the tire 31, a device is provided for making the incision 35 to which a rotation is applied about an axis to create the inclination of the incision within the meaning of the present invention. Because of the S-shape of the incision 35 and the shape of the tire, especially its axial curvature, this axis of rotation is not tangent, which at the point of the incision, which leads to a continuous variation of the angle over the entire length of the incision as shown by the values measured above.

[00101] In Figures 4a and 4b a partial perspective view of a tire 41 is shown, similar to that of Figures 2 and 3, and which differs by the presence of a substantially meridian incision 45 whose orientation varies between the central portion of the tire and axially outer parts.

[00102] In fig. 4a, a meridian plane 46 and the equatorial plane 47 are shown whose intersection forms a straight line 48 radially oriented and cutting incision 45 at a point B on the tread surface 42.

[00103] Line 48 forms an angle β at point B with curve 49, which represents the intersection of the equatorial plane 47 with incision 45. This angle β has a value of 10 °.

[00104] Figure 4b illustrates an angle β 'at point B' between a line 49 'and a curve 48 these curves are defined as in the case of figure 4a, more from another circumferential plane 47' translated axially with respect to equatorial plane 47 and another meridian plane 46 'translated circumferentially with respect to plane 46 of fig 4a such that line 48' cuts incision 45 at point B 'of the tread surface 42. The angle β' has a value -10 °. The negative sign is indicated to show the opposite direction to that of the angle β.

[00105] In accordance with one of the variants of the invention, one of these angles is oriented according to the direction of travel of the tire and the other in the reverse direction. These orientations in the opposite direction to the incision 45 inclination will a priori have opposite effects on the handlebar efforts as the pilot drives in a straight line depending on whether the driver is driving in a straight line or in a curve, since the nature of the polymeric compounds and architecture are homogeneous over the entire axial width of the tire 41 or at least the axial width of the incision 45.

[00106] The invention should not be understood as being limited to the examples described above. It notably provides the combination of the various embodiments of the invention illustrated in the figures with the polymeric compounds of the tread and / or architectures, which may vary according to the axial direction and, especially, with tires comprising tread made up of different compounds polymeric depending on the axial position, the layers of reinforcement elements oriented circumferentially, whose pitch varies according to the axial direction and the angles of elements of the reinforcement of the working layers which vary according to the axial direction.

[00107] The invention should also not be understood as being limited in the case of a tire intended to equip the front wheel of a motor vehicle with two wheels, but it may be of interest for a rear wheel. Indeed, the presence of incisions according to the invention can also affect the tire wear profile and, under certain conditions of use, they can have an effect on the behavior of the tire during motor driving or braking passages.

[00108] The tests were carried out with a tire of dimension 120/70 ZR 17 carried out according to the case reported in figures 4a and 4b, a positive angle corresponding to the tire's direction of roll.

[00109] This tire was compared to two reference tires identical to the tire of the invention, if not the total absence of incisions in the tread of the tire R1 and the presence of incisions without inclinations and, thus, radially oriented to the tire R2 . The number of incisions is identical on the same tire according to the invention and the reference tire R2.

[00110] The tests consisted of carrying relative notes on the various maneuvers, of said tires being mounted on the same motorcycle and piloted by the same rider, in the same conditions to obtain the evaluations when accelerating or braking around three angles of curvature different, corresponding respectively to 10 °, 20 ° and 30 °.

[00111] The results are given in the table below:

[00112] The results of the R2 tire show first that the presence of not inclined incisions, as proposed by the invention has no effect on the return of efforts on the handlebars.

[00113] The values obtained with the tire according to the invention led to a tire more convenient than the reference tires R1 and R2 on strong curvature (inclination) and less convenient with a low curvature (inclination) and then on a straight line.

Claims (13)

Tire for a two-wheel motor vehicle comprising:
a carcass type reinforcement structure, formed by reinforcement elements, anchored on each side of the tire to a bead whose base is intended to be mounted on a rim base, each bead extending radially outwards by a flank, the flanks radially towards the outside joining a tread, characterized by the fact that
the tread comprises at least one incision, in which in a circumferential plane, at least a portion of a wall of said at least one incision forms an angle between the radial direction between 5 and 45 °,
the angle formed between at least a portion of a wall of said at least one incision and the radial direction in a first circumferential plane is different from the angle formed between at least a portion of said wall of at least one incision and the radial direction in at least one second circumferential plane,
the tread comprises at least one incision, in which in a circumferential plane, at least a portion of a wall of said at least one incision forms an angle between the radial direction between 5 and 45 °,
the angle formed between at least a portion of a wall of said at least one incision and the radial direction in a first circumferential plane is different from the angle formed between at least a portion of a wall of said at least one incision and the radial direction in at least one second circumferential plane,
the tread comprises a central part and its axially outer parts defined by respective circumferential grooves, in which at least one incision passes through the central part and opens within the respective circumferential grooves, and
said tire has a curvature greater than 0.15, where the curvature is defined by a ratio Ht / Wt, where Ht is a height of the tread and Wt is a maximum width of the tire's tread. Tire according to claim 1, characterized by the fact that said at least a portion of said at least one incision that forms with the radial direction an angle between 5 and 45 ° is in contact with the area of contact with the ground. Tire according to claim 1, characterized by the fact that the difference between the angle formed between at least a portion of a wall of said at least one incision and the radial direction in a circumferential first plane and that formed in at least one second circumferential plane is greater than 10 °. Tire according to claim 1, characterized by the fact that said at least one incision forms at least locally with the circumferential direction an angle greater than 70 °, in which the angle formed between at least a portion of a wall of said at least one incision and the radial direction is less than 30 °. Tire according to claim 1, characterized by the fact that said at least one incision forms at least locally with the circumferential direction an angle less than 30 °, in which the angle formed between at least a portion of a wall of said at least one incision and the radial direction is greater than 35 °. Tire according to claim 1, characterized in that the orientation of the angle formed between at least a portion of a wall of said at least one incision and the radial direction is the same in the direction of rotation of the tire. Tire according to claim 1, characterized by the fact that at least the surface of the tread consists of a first polymeric compound extending over at least a portion of the central part and at least a second polymeric compound having physico-chemical properties. different from those of said first polymeric compound and covering at least a portion of the axially outer parts of the tread. Tire according to claim 1, characterized by the fact that the difference between the angle formed between at least a portion of a wall of said at least one incision and the radial direction in a circumferential first plane passing through the central part and that formed in a second circumferential plane belonging to an axially outer portion it is greater than 10 °. Tire according to claim 1, characterized by the fact that the reinforcement elements of the carcass type reinforcement structure form an angle between 65 ° and 90 ° with the circumferential direction. Tire according to claim 1, characterized in that the reinforcement structure of the crown comprises at least one layer of reinforcement elements, known as the working layer, and in which the reinforcement elements form angles between the circumferential direction between 10 and 80 °. Tire according to claim 10, characterized in that the angles formed by the reinforcement elements of said at least one working layer with the longitudinal direction can vary in the transverse direction. Tire according to claim 1, characterized in that the crown reinforcement structure comprises at least one layer of circumferential reinforcement elements. Tire according to claim 12, characterized in that the circumferential reinforcing elements are distributed in the transverse direction in a variable pitch.

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